Celery redis backend does not unsubscribe from

The Fix

pip install celery==4.4.0rc5

Based on closed celery/celery issue #4707 · PR/commit linked

Production note: Most teams hit this during upgrades or environment changes. Roll out with a canary and smoke critical endpoints (health, OpenAPI/docs) before 100%.

Jump to Verify Open PR/Commit

@@ -711,6 +711,8 @@ def send_task(self, name, args=None, kwargs=None, countdown=None,
                 'task_always_eager has no effect on send_task',
             ), stacklevel=2)
+
+        ignored_result = options.pop('ignore_result', False)
         options = router.route(

repro.py

"""Celery tasks module."""
from celery import Celery
from kombu import Queue
from redis import StrictRedis
from time import sleep

class CeleryConfig(object):
    # celery configurations
    broker_url = 'redis://localhost:6379/1'
    task_default_queue = 'default'
    task_queues = (
        Queue('default', routing_key='parent.#,opbeat'),
    )
    imports = ('tasks',)
    result_backend = 'redis://localhost:6379/2'

def create_app(config):
    """Create a celery app instance."""
    celery_app = Celery("tasks")
    celery_app.config_from_object(config)
    return celery_app

app = create_app(CeleryConfig)

@app.task(ignore_result=True)
def enrich_single_call(data):
    """Single call to task that returns nothing. """
    pass

def run_test_task():
    """Run test task."""
    redis = StrictRedis()
    channels_before = len(redis.execute_command('PUBSUB CHANNELS'))
    print('Redis channels count before task execution {}'.format(channels_before))
    result = enrich_single_call.delay('hello')
    sleep(5)
    channels_after = len(redis.execute_command('PUBSUB CHANNELS'))
    print('Redis channels count after execution {}'.format(channels_after))

verify

Re-run the minimal reproduction on your broken version, then apply the fix and re-run.

fix.md

Option A — Upgrade to fixed release\npip install celery==4.4.0rc5\nWhen NOT to use: This fix should not be used if task results are required to be retrieved.\n\n

Why This Fix Works in Production

Trigger: redis backend does not unsubscribe from celery-task-meta-XXX channels when ignore_result=True
Mechanism: The Redis backend was not unsubscribing from channels when task results were ignored, leading to resource issues
Why the fix works: The fix prevents unnecessary Redis channel subscriptions when task results are ignored, addressing resource issues caused by growing subscriptions. (first fixed release: 4.4.0rc5).

Production impact:

If left unfixed, the same config can fail only in production (env differences), causing startup failures or partial feature outages.

Why This Breaks in Prod

The Redis backend was not unsubscribing from channels when task results were ignored, leading to resource issues
Production symptom (often without a traceback): redis backend does not unsubscribe from celery-task-meta-XXX channels when ignore_result=True

Proof / Evidence

GitHub issue: #4707
Fix PR: https://github.com/celery/celery/pull/4709
First fixed release: 4.4.0rc5
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.42

Discussion

High-signal excerpts from the issue thread (symptoms, repros, edge-cases).

Jump to Sources Open on GitHub

“@mleginus this issue has been closed for some time now. Would you mind opening a new issue, so that we can continue the discussion there?…”

@georgepsarakis · 2018-06-18 · source

“I think I found the root cause and managed to solve this, but I need to consider my solution once more. I will certainly follow…”

@georgepsarakis · 2018-05-05 · source

“@bartloop if possible, please provide some feedback on the potential fix. Thank you!”

@georgepsarakis · 2018-05-05 · source

“@bartloop if you think that the documentation can be expanded, to help avoid similar issues in the future, please feel free to open a Pull…”

@georgepsarakis · 2018-05-06 · source

Failure Signature (Search String)

redis backend does not unsubscribe from celery-task-meta-XXX channels when ignore_result=True
If the unsubscribe doesn't happen, the list of subscriptions grows without end, causing resource issues after several hundred thousand tasks.

Copy-friendly signature

signature.txt

Failure Signature
-----------------
redis backend does not unsubscribe from celery-task-meta-XXX channels when ignore_result=True
If the unsubscribe doesn't happen, the list of subscriptions grows without end, causing resource issues after several hundred thousand tasks.

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
redis backend does not unsubscribe from celery-task-meta-XXX channels when ignore_result=True
If the unsubscribe doesn't happen, the list of subscriptions grows without end, causing resource issues after several hundred thousand tasks.

Minimal Reproduction

repro.py

"""Celery tasks module."""
from celery import Celery
from kombu import Queue
from redis import StrictRedis
from time import sleep

class CeleryConfig(object):
    # celery configurations
    broker_url = 'redis://localhost:6379/1'
    task_default_queue = 'default'
    task_queues = (
        Queue('default', routing_key='parent.#,opbeat'),
    )
    imports = ('tasks',)
    result_backend = 'redis://localhost:6379/2'

def create_app(config):
    """Create a celery app instance."""
    celery_app = Celery("tasks")
    celery_app.config_from_object(config)
    return celery_app

app = create_app(CeleryConfig)

@app.task(ignore_result=True)
def enrich_single_call(data):
    """Single call to task that returns nothing. """
    pass

def run_test_task():
    """Run test task."""
    redis = StrictRedis()
    channels_before = len(redis.execute_command('PUBSUB CHANNELS'))
    print('Redis channels count before task execution {}'.format(channels_before))
    result = enrich_single_call.delay('hello')
    sleep(5)
    channels_after = len(redis.execute_command('PUBSUB CHANNELS'))
    print('Redis channels count after execution {}'.format(channels_after))

What Broke

The number of Redis pubsub channels grew indefinitely, causing resource exhaustion.

Why It Broke

The Redis backend was not unsubscribing from channels when task results were ignored, leading to resource issues

Fix Options (Details)

Option A — Upgrade to fixed release Safe default (recommended)

pip install celery==4.4.0rc5

When NOT to use: This fix should not be used if task results are required to be retrieved.

Use when you can deploy the upstream fix. It is usually lower-risk than long-lived workarounds.

Fix reference: https://github.com/celery/celery/pull/4709

First fixed release: 4.4.0rc5

Last verified: 2026-02-09. Validate in your environment.

When NOT to Use This Fix

This fix should not be used if task results are required to be retrieved.

Verify Fix

verify

Re-run the minimal reproduction on your broken version, then apply the fix and re-run.

Did This Fix Work in Your Case?

Quick signal helps us prioritize which fixes to verify and improve.

Prevention

Capture the exact failing error string in logs and tests so you can reproduce via a minimal script.
Pin production dependencies and upgrade only with a reproducible test that hits the failing path.

Version Compatibility Table

Version	Status
4.4.0rc5	Fixed

Related Issues

No related fixes found.

Cluster: celery:configuration-error Celery hub Celery best practices All hubs All clusters

Related clusters: Data consistency Duplicates Duplicate processing

Sources

We don’t republish the full GitHub discussion text. Use the links above for context.

Celery redis backend does not unsubscribe from celery-task-meta-XXX channels when ignore_result=True (Fix)